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Blower vents & temperature problems


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Anonymous Poster
patrickmcgrath@charter.net

Aug 31, 2009, 2:59 PM

Post #1 of 8 (2431 views)
Blower vents & temperature problems Sign In

I have a 2003 Jeep Grand Cherokee 6 Cyl. 4.0L has around 114,000 mile.
For a while I noticed that when I put the fan on and set it on cool, it will feel warm or even hot (not normal). Recently, when I have it set on blowing out the vents, it will switch from blowing at me, then blow from the floor vents and the vents on the windshield (defrost vent), then switch back at blowing back at me.
What would cause this?


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Aug 31, 2009, 9:02 PM

Post #2 of 8 (2423 views)
Re: Blower vents & temperature problems Sign In

The mode selection is done through a series of air doors that are operated by vacuum. When there is either a partial or total loss of vacuum, the system will default to either defrost or on some vehicles, heat. Acceleration can also have an effect on the doors for the same reason.

Look under the hood for a small black plastic hose coming through the firewall. Follow it to the vacuum source looking for any breaks, cracks or leaks. Also follow any other lines that branch off because they may go to a vacuum resevoir (storage tank) and a leak there will cause the same problem. Using a vacuum gauge to determine if you have full vacuum at any given point is the best way to find it. You can cut into the line anywhere and splice it back together with a piece of vacuum hose. Find the broken line, you found your problem.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



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Anonymous Poster
patrickmcgrath@charter.net

Sep 1, 2009, 1:20 PM

Post #3 of 8 (2413 views)
Re: Blower vents & temperature problems Sign In

I was told I don't have a vacuum system for that problem; I was told it's an electrical issue pertaining to it. I would have to change the 3 knob controls which is a little pricey. I would assume that would affect the blowing out the correct vents when selected. Tell me if I misunderstood or the other person misunderstood what I was saying orif I was given bad advice.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Sep 1, 2009, 1:25 PM

Post #4 of 8 (2409 views)
Re: Blower vents & temperature problems Sign In

Actually, I should have asked if you had an auto temp control system of manual. The auto system uses electric and the manual system uses vacuum.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



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Anonymous Poster
patrickmcgrath@charter.net

Sep 1, 2009, 1:40 PM

Post #5 of 8 (2404 views)
Re: Blower vents & temperature problems Sign In

Temp. control I would guess is manual. I turn the knob all the way left (blue ) for cool and I can turn it all the way right (red) for hot.... and anywhere in between.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Sep 1, 2009, 1:41 PM

Post #6 of 8 (2401 views)
Re: Blower vents & temperature problems Sign In

OK, then my first answer stands...........



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Guest
Anonymous Poster

Sep 1, 2009, 2:30 PM

Post #7 of 8 (2396 views)
Re: Blower vents & temperature problems Sign In

OK Thanks for the advice. I will check that and hope that keeps the selected vents will stay on what I selected and when I put it on fan or cool it will stay cool.
I'll throw this at you. I have a co-worker who has a show winning 1969 I believe Camaro..... I guess he knows about the older cars he says. He says he uses a fuel system cleaner called Lucas which he uses once a month. He says it's like a tune up in a bottle too. He said for me to try it to clean the injectors in my Jeep. I have always used STP or Gumout. Which is better? Or does it really matter; they all work the same.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Sep 1, 2009, 8:54 PM

Post #8 of 8 (2387 views)
Re: Blower vents & temperature problems Sign In

I will agree that Lucas is probably the best additive out there but don't expect any additive to correct any existing problem. They may work sufficiently to be a preventative but none of them will correct a problem once it's there.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.







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